Heretofore, relatively thick, water-permeable fiber layers formed of a double knitted fabric made by the double Raschel machine or a non-woven fabric or the like have been embedded to protect the faces of slopes in residential sites, created land, dikes or the like and to impart a water collecting and discharging effect thereto.
However, with such non-woven fabric, double knitted fabric or the like, the load of fill-up earth acts on the entire fiber layer, with the result that the fiber layer is compressed to cause a decrease in the void content thereof; thus, there is a drawback that the water collecting and discharging effect is spoiled. Further, the fill-up earth is divided into two vertically spaced layers, above and below the fiber layer. The upper fill-up earth tends to slide more easily and if planting is made on this upper fill-up earth, there is another drawback that the growth of the roots of the plant is impeded by the fiber layer. Further, with the usual double knitted fabric, the amount of fiber to be used increases, leading to a high cost and making the fiber layer heavier and difficult to handle, degrading the quality of operations, such as embedding and taut spreading of the net.
Further, of the nets used as slope face protecting nets, planting nets, building protecting nets or the like, many have their cord portions, which define the meshes, made of cords or wires which are solid. Further, knitted fabrics of three-dimensional mesh are also available; in this case also, the cord portions which define the meshes are nothing but those which define a simple wall. Therefore, such net is relatively heavy and difficult to handle, and its cord portions cannot be expected to provide ventilating and water collecting and discharging effects.